Invisible Bubbles

Objective / Question / Problem
Determine the effects on metal foil and sheet metal for immersion in ultrasonic cleaner. Quantify if possible.
Questions : Was material removed in test ? What materials are effected ? Where does the removed materials go ? How to  determine how much material is removed per unit of time. What prevents all materials from being removed by sonic energy ?

Hypothesis
Warnings by manufacture indicate leaving some materials to long in tank indicate material could be removed.
Initial 40 second immersion test of Aluminum foil indicates the 0.001( one thousandth) inch thickness will hole through

Test Set Up & Materials
* Ultasonic  Jewelry or Denture Cleaner . Size: 6 oz ( approx. 2 coffee cups ). Frequency: 42,000 cycles per second ( 42K cps) as built. Mfg: MPI Industries Inc. in Springfield, MI in abt. 1970.
Test Materials:
* Household Aluminum foil (1 thousanth of an  inch think) Renolds Foil # 657.
* Aluminum sheet ( 4 thousanths of an inch think) scissors cut from soda can.
* Suran Wrap @ 1 thousanth of an inch thick.
* Fiberglass Tape @ 4 thousanths of an inch thick
* Steel coffee can lid @ 9 to 13 thousanths of an inch thick.
Othe Materials::
* Sandpaper
* Scotch tape
* Watch or clock with seconds shown
* Tap water from home faucet
* Thickness data on materials used or micrometer to measure its thickness.

Safety
Note, putting hand or fingers in this or likely very small similar ultrasonic tank with water is safe for short periods. It feels like very tiny fish nibbling or tingling at your fingers!

Sources: Ultrasonic Cleaning Companys' web site pages.One is Branson Co.

Instructions
Fill ultrasonic cleaner tank with tap water to almost top. Do not get water down into device.
Material samples must be smaller than tank to get them in. Use 1-1/1/2 inch wide strips  and 2-3 inch long.
Hand hold and count seconds or time for each test. Suspend by still hand or clamp. You should hold sample still during test.
Immerse samples of foil in tank with out contacting ( touching) edges or bottom while running cleaner. This is to not influence test with direct coupling of energy from tank wall. Time the immersion till it holes through or long enough to determine it is not effected and record. Observe pin holes using back lighting.

Mask a sample foil section of known area ( 1 inch square) & time to completely gone and record time.
 

Independent Variables: Time
Dependent Variable Material Removed
Controlled Variable: Type of Material Sample & Thickness
 

Results
* For thin foil of 1 thousanth of an inch , it pin holes through at  5 seconds & visibly holes through at 20 second without aided back lighting..
* Soda can aluminum sheet of 4 times thicker 4 thousanths of inch does not seem effected, even with both paint ( outside) & plastic coating ( inside) removed by sandpape based on no visible pimples at several minutes exposure..
* Scotch tape seems to be a barrier that protects the aluminum foil from effects.
* One inch square ( masked foil test) removal was not linear, most of the area in a ring was removed in first few minutes.
* Filtering of used tank water resulted in catching Aluminum particles.

Conclusions
* Scotch tape protects foil from Ultrasonic energy.
* Sheet Aluminum is not effected by ultrasonic energy even with coatings removed.
* Ultrasonic energy does not effect plastic and plastic tape protecks foil from bubble energy.
* Thin Aluminum foil pin holes through very quickly.
* Aluminum material removed can be filtered out with paper filter, even though it is to fine to see in suspension.
* Circular ring shape of area being removed on foil indicates energy area is not constant on full surface and is likely reason square masked area removal was not linear in time.
* A better way is needed to measure amount of material per unit of time.
Photographs
Aluminum Foil Samples All shown on sheet in B&W
Aluminum Foil Samples All Shown on sheet in Color
Aluminum Foil Sample for 5 Seconds Immersion
Aluminum Foil  Sample for 40 Seconds Immersion
Student Holding Sample in Ultrasonic Tank
Student Holding Finger in Tank to Show its Safe for Short Exposures